Resilient by nature: Managed rearing does not erode physiochemical tolerances of an extremophile fish

Populations in managed care are valuable resources that complement in situ conservation efforts, but adaptation to captive conditions and other domestication effects present concerns for conservation. Many populations of fish adapted to sulfide springs are highly endemic and imperiled, potentially benefiting from ex situ conservation efforts. However, it is challenging to maintain natural conditions in the laboratory as hydrogen sulfide (H2S) is highly toxic and coincides with severe hypoxia. Here, we tested whether long-term standardized rearing of sulfide spring fishes leads to the loss of H2S and hypoxia tolerances. We compared the tolerances of Poecilia mexicana (Poeciliidae) from sulfidic and non-sulfidic habitats that were reared in the laboratory for 18 years and wild-caught fish from the same sites. Both H2S and hypoxia tolerances were maintained in laboratory-reared fish from the sulfidic habitat. Additionally, fish from a non-sulfidic cave site, evolutionarily derived from a s..., , # Resilient by nature: Managed rearing does not erode physiochemical tolerances of an extremophile fish Dataset DOI: [10.5061/dryad.4qrfj6qqg](https://doi.org/10.5061/dryad.4qrfj6qqg) ## Description of the data and file structure This dataset includes measures of hypoxia and hydrogen sulfide tolerance in laboratory-reared and wild-caught populations of *Poecilia mexicana* (Lab_adapted_loe.xlsx) and environmental conditions at the collection site measured in 2025 (env_2025.xlsx). The two Excel files are analyzed using the R script LOE_labadapted_final.Rmd. ### Files and variables #### File: Lab_adapted_loe.xlsx **Description:** This dataset includes information on the tolerance trials for wild-caught and laboratory-reared fish. ##### Variables: * Date: Date of trial * Time: Time of trial * Trial: Trial number * Trial_Type: Type of trial (hypoxia tolerance or hydrogen sulfide tolerance) * Pop: Population= PS5, Luna, PS10, PS2, Oxo, PS13, Bonita * LOE: time until loss of equi...,